This vast underground vaulted hall was part of the fortified castle built in 1514. It was probably a weapons room before being used as a water reservoir. The underground chamber, measuring 34 meters by 34 meters, was constructed with five rows of five stone pillars. The cistern is famous especially for the thin layer of water that covers the floor, and which creates fine and exciting reflections from the little light there is and the spartan shapes of the columns and the roof.I